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Open Roads Forum  >  Class A Motorhomes  >  Maintenance Issues & Tips

 > 93 Brave with Chevy 454 acceleration issuea

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Solo

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Posted: 03/07/18 04:21am Link  |  Print  |  Notify Moderator

You've been given good advice already and must determine whether your 7.4L has been altered with a carburetor or is actually TBI. From there, you will have a much better path to diagnosis. Assuming you have the original TBI, I would be throwing darts at your problem by simply suggesting replacing parts without looking at the OBD I data stream and checking fuel pressure. If you don't have the equipment or experience, find someone who can otherwise, part swapping just for the sake of trying to get lucky may be a frustrating endeavor.


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1995brave

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Posted: 03/07/18 06:04am Link  |  Print  |  Notify Moderator

When was the last time the in-line fuel filter was changed? Also check all the rubber hoses around the TBI being that old they are probably all rotted or dried out causing vacuum leaks. Good time to check everything on the top end and clean the TBI. When I picked up my 95 Brave in 2005 a lot of the hoses were loose and dried out, replaced them all along with cleaning the TBI and replacing the gaskets and filters. Ran 100 times better.

psalm10720

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Posted: 03/07/18 07:12am Link  |  Print  |  Notify Moderator

Fuel lines and vacuum lines replaced. Why is it hard to believe it’s carbureted? It is.

Blutoyz

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Posted: 03/07/18 07:20am Link  |  Print  |  Notify Moderator

psalm10720 wrote:

Fuel lines and vacuum lines replaced. Why is it hard to believe it’s carbureted? It is.


If it is and it is running well cold (auto choke closed) then you have a starting point. Check fuel pressure first, check accel pump (not running of course), and if you are handy...just do a rebuild/refresh on it. It is a cheap kit and will force you to clean it well when you do the rebuild.

Just my $.02


She may be old but she is paid for (the rig that is)


1995brave

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Posted: 03/07/18 07:26am Link  |  Print  |  Notify Moderator

If it has a carb, it should not have an ECM. Remove the carb and have it rebuilt, the jets are probably gummed up along with the accelerator pump diaphram. Take it to a good old school mechanic the new kids don't know what a carb is. Also check the fuel filter on the gas inlet on the carb.

enblethen

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Posted: 03/07/18 09:41am Link  |  Print  |  Notify Moderator

Many original sensors and ECM would have to be removed.
Not sure how changing TBI to carb would effect the fuel pump.

* This post was edited 03/07/18 10:09am by enblethen *


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psalm10720

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Posted: 03/07/18 11:14am Link  |  Print  |  Notify Moderator

I’m not a mechanic and hopefully a good mechanic can ferret out the problem. I was hoping someone dealt with the same issue. I have done much work to this RV. Total new vacuum lines, water pump, engine a/c pump, radiator etc.. I have an apt the beginning of April to drop off at a old school speed shop. Chevy truck center didn’t have any carb savvy techs. Big RV stores like Lazydays charge $149.00/hour. Hopefully a competent carb savvy tech can ferret out the real problem. I’ll make sure to list all the possibilities mentioned. Will post result. Won’t be til mid-April. Thanks

tderonne

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Posted: 03/07/18 11:36am Link  |  Print  |  Notify Moderator

A good mechanic (who knows carburetors) is a good call. As others have said, Chevrolet made the last carbureted 454s in 1989. If you have a carb, it probably isn't stock, and probably just needs some good ol' fashioned tuning. Remember LOTS of mechanics you'll find weren't even born in 1989 (someone born in 1989 is turning 29 this year). I was asked yesterday if an "alternator" is that thing that cars don't have anymore. I corrected her and said that was a "carburetor".

You should be able to find your RPO code somewhere, it ought to be L19. That'd tell you for sure it was TBI at some point.

Some 454 info (updating my post):

RPO LE8: 240 net hp (trucks only)
Small oval (“peanut”) port cast-iron heads, Quadrajet 4-barrel carb, mild hydraulic lifter cam, two- or four-bolt main caps, cast-iron crankshaft. Available in trucks only through 1986 and some heavy trucks through 1989.

RPO L19: 230 net hp (trucks only)
This engine superseded the LE8 when General Motors switched from carburetors to computer-controlled 2-barrel TBI (throttle body injection) in 1987. Small oval (“peanut”) port cast-iron heads, mild hydraulic lifter cam, two- or fourbolt main caps, cast-iron crankshaft. Available in trucks only from 1987 to 1990, this was the last production Mark IV engine.

7.4 Liter Gen V (454 ci) RPO L19: 230 net hp (trucks only)
Even though General Motors switched to the newly designated Gen V block, heads, and crankshaft in 1991, this workhorse retained the same RPO number as its predecessor: small oval (“peanut”) port cast-iron heads, TBI, mild hydraulic lifter cam, four-bolt main caps, cast-iron crankshaft. Available in trucks only from 1991 to 1995.

7.4 Liter Gen VI (454 ci) RPO L19/L29: 290 net hp at 4,000 rpm (trucks only)
The Vortec 7400 featured more refinements including the use of MPFI (multi-point fuel injection) and hydraulic roller lifters: small oval (“peanut”) port cast-iron heads, four-bolt main caps, cast-iron crankshaft. Available in trucks only from 1996 to 2000.

* This post was edited 03/07/18 11:47am by tderonne *


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psalm10720

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Posted: 03/07/18 11:44am Link  |  Print  |  Notify Moderator

The alternator on my gold wing f6b is huge for a bike.

Brian in Michigan

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Posted: 03/07/18 02:04pm Link  |  Print  |  Notify Moderator

My 1990 is a 1989 chassis. It was the very last of the carburetors. When I had my buddy rebuild it he had a difficult time getting the right parts.


1990 GEORGIE BOY 28' 454 4BBL, TURBO 400 TRANS, Thorley Headers B&M trans cooler. Flowmaster mufflers recurved distributor Still Keepin on Truckin((((Was 7.5mpg Now 8.75mpg ))))

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